interface A {
double f(double x,double y);
}
class B implements A {
public double f(double x,double y) {
return x*y;
}
int g(int a,int b) {
return a+b;
}
}
public class E61 {
public static void main(String args[]) {
A a = new B();
System.out.println(a.f(3,5));
B b = (B)a;
System.out.println(b.g(3,5));
}
}
